Gentamicin is a bactericidal aminoglycoside antibiotic derived from Micromonospora purpurea. It is a broad-spectrum antibiotic primarily effective against aerobic Gram-negative bacilli, including Pseudomonas aeruginosa, and some Gram-positive organisms like Staphylococcus aureus. In the Indian context, it is a critical, cost-effective agent for severe infections, but its use is tempered by the risk of nephrotoxicity and ototoxicity, necessitating therapeutic drug monitoring (TDM) where available.
Adult: Conventional dosing: 3-5 mg/kg/day in 2-3 divided doses (e.g., 80 mg IV/IM every 8 hours). Extended-Interval (Once-Daily) Dosing: 5-7 mg/kg as a single daily dose. MUST be guided by TDM and clinical condition.
Note: For IV use: Dilute in 50-100 mL of 0.9% Sodium Chloride or 5% Dextrose. Infuse over 30-60 minutes. NEVER give as IV bolus (risk of neuromuscular blockade). For IM use: Administer deep into a large muscle mass. Monitor peak levels 30 minutes after end of IV infusion or 60 minutes after IM injection. Monitor trough levels just before the next dose.
Gentamicin binds irreversibly to the 30S ribosomal subunit of susceptible bacteria, specifically to the 16S rRNA and proteins of the A-site. This binding interferes with the initiation complex, causes misreading of the mRNA template, and inhibits translocation. The result is the incorporation of incorrect amino acids into the growing peptide chain, leading to the production of non-functional or toxic proteins and ultimately bacterial cell death.
Pregnancy: Category D (US FDA). Aminoglycosides cross the placenta. Risk of fetal ototoxicity (8th cranial nerve damage) exists. Use only if potential benefit justifies the potential fetal risk, typically for life-threatening maternal infections.
Driving: Patients should be cautioned that gentamicin can cause dizziness, vertigo, and visual disturbances, which may impair the ability to drive or operate machinery, especially if ototoxicity develops.
| Other Nephrotoxic drugs (Vancomycin, Amphotericin B, Cisplatin, NSAIDs, Loop diuretics) | Additive or synergistic nephrotoxicity | Major |
| Other Ototoxic drugs (Furosemide, Ethacrynic acid, Cisplatin) | Additive or synergistic ototoxicity | Major |
| Neuromuscular blocking agents (Succinylcholine, Tubocurarine) | Enhanced and prolonged neuromuscular blockade, leading to respiratory depression/apnea | Major |
| Penicillins (e.g., Carbenicillin, Ticarcillin) when mixed in vitro | Physical inactivation of gentamicin; administer separately. | Moderate |
| Indomethacin in neonates | May increase gentamicin levels and toxicity risk | Moderate |